Fast food isn't making our kids fat. It's the rest of their diet.

If you closed all the fast-food restaurants, would fewer U.S. kids be fat? A new study says no.

If you closed all the fast-food restaurants, would fewer U.S. kids be fat? A new study says no. (AFP/Getty Images)

Melissa Healy

Imagine for a moment that all of the nation's fast-food establishments--all the striped awnings and golden arches, the drive-thru windows, the beckoning dollar deals and wafting odor of French fries--were to vanish overnight. Would the number of our kids who carry an unhealthful amount of extra weight plummet?

The answer is very likely no, says a study published Thursday in the American Journal of Clinical Nutrition. Because if you shut off the supply of 24-ounce fountain drinks, bacon cheeseburgers, fried chicken and stuffed tacos, the children who frequently eat at fast-food restaurants will go home and do what they generally do when not eating at a fast-food restaurant: They'll snarf cookies and chips, chug sugar-sweetened soda from a bottle, and heat up frozen pizzas.

In a new study, researchers from the University of North Carolina led by nutrition professor Barry Popkin have found that even when they are not eating at fast-food restaurants, children who frequent them tend to eat food that would probably make many of them overweight or obese anyway. The authors of the latest research combed through a national database of Americans' health and nutrition behaviors and grouped 4,466 American kids--from ages 2 to 18--according to what they ate when they were not eating food purchased at a fast-food restaurant.

Participants were designated "Western diet" consumers if their consumption from non-fast-food sources was relatively high in saturated fats and added sugars. Those classified as following a "prudent diet" ate more fruits and vegetables, leaner proteins and less added sugar and saturated fat.

After doing so, they went back to the children's detailed food consumption records and categorized them as nonconsumers of fast food (those whose food tracking records indicated no calories consumed from a restaurant or eating establishment without servers), low consumers (whose food tracking records indicated that no more than 30% of their calories came from such an establishment), and high consumers (for whom more than 30% of calories consumed came from a fast-food restaurant).

The result: Those who followed the Western dietary pattern when not dining at fast-food restaurants--even those who were considered "nonconsumers" of fast food--had the highest rates of being overweight or obese. Those who followed a "prudent diet" when not dining on fast food--even those who were considered high consumers of fast food--were significantly less likely to be overweight or obese.

On average, low consumers of fast food were 1.5 times as likely to follow a Western diet pattern of consumption than people who were considered nonconsumers of fast food. High consumers of fast food were 2.2 times as likely to do so.

"Our findings suggest that the location where foods are obtained may not be as important as the nutritional quality of the foods consumed," the authors wrote. They also suggest that "the effect of public health efforts targeted at fast food restaurants may also be overestimated, such that these efforts may be necessary but not sufficient to reduce child obesity if the remainder of the diet is not addressed."

The study was sponsored by the Robert Wood Johnson Foundation, and the authors--Jennifer M. Poti, Kiyah J. Duffy and Popkin--declared they had no financial conflicts of interest with respect to the article.